Balloons coated with paclitaxel containing formulations are known. In some cases paclitaxel has been applied directly to the balloon or to a coating placed on the balloon. In other cases paclitaxel has been formulated with an excipient that may be polymer, a contrast agent, a surface active agent, or other small molecules that facilitate adhesion to the balloon and/or release from the balloon upon expansion. The formulations have typically been applied from solution, and may be applied to the entire balloon or to a folded balloon, either by spraying, immersion or by pipette along the fold lines.
Paclitaxel coated balloons that provide high release rates from the balloon surface have recently been developed. However these balloons do not yet provide for delivery of predictable amounts of the drug to the tissue at the delivery site nor do they provide for a predictable therapeutic drug tissue level over an extended time period.
In regards to drug delivery from a balloon, currently a mixture of a drug (paclitaxel) and a secondary substance in solution is sprayed or dip-coated on a balloon surface and dried, creating a solid matrix of the two components on the balloon surface which breaks off in undefined and sometimes very large pieces upon deployment of the balloon. These pieces can be up to hundreds of micrometers. A variety of negative effects can as such be described.                a/ The distribution of the particles over the vessel wall is non-uniform. Having large chucks at one place automatically means a void at other places.        b/ The uptake into the tissue is different as it is known that single micrometer sized and nano-sized particles are better absorbed by cells. So, with the current matrix breaking up in a wide distribution of chunks part will be absorbed and part will hang on the wall or float downstream.Furthermore having the drug being sprayed in solution causes the drug to be present in the final coating on the balloon surface in an unknown mixture of amorphous and crystalline nature. It is known, however, that a crystalline or amorphous morphology of paclitaxel greatly affects the extended release kinetics of the drug in tissue.        